In a separate written statement, Pataki called Rubio the candidate most likely to defeat Hillary Clinton in a general election.

"I fear if Donald Trump is our party's nominee, then Hillary Clinton will be President," he said. "Fortunately, Republicans who want to win have a conservative alternative in Marco Rubio – a person who will not only unite our party, but defeat Hillary Clinton in November."

Pataki failed to gain traction during his own presidential bid, polling only in the low single digits and consistently missing the threshold for participation in primetime GOP primary debates.

Former Arizona Sen. Jon Kyl also endorsed Rubio earlier this week.

Pataki's announcement comes one day after former Texas governor Rick Perry, another former 2016 hopeful, endorsed Ted Cruz as the next commander-in-chief. Perry will campaign with Cruz in Iowa this week.